The present invention relates generally to electronic power converters and, more particularly, to a system and method for determining a single-phase and/or three-phase current in power converters, either input current to the converter or output current from the converter, as particularly suited for use with variable speed drives.
Power converters are electrical or electro-mechanical devices for converting electrical energy. Power converters can thus take the form of AC-AC converters that convert one AC waveform to another AC waveform with a desired voltage and frequency, or take the form of DC-AC inverters that invert DC power to an AC power having a desired voltage and frequency. Power converters can be implemented in single-phase or three-phase systems, for example, to provide such a desired power conversion.
One type of system commonly used in industry that performs power conversion is an adjustable or variable speed drive (VSD), which is an industrial control device that provides for variable frequency, variable voltage operation of a driven system, such as an AC induction motor. In many existing VSDs, Hall-effect current sensors, CTs and shunts are used for performing measurements of the three-phase output current of the VSD. However, such current measurement devices are expensive, sensitive to environmental conditions, and occupy a large amount of system “real estate” or space. Thus, even though Hall-effect current sensors, CTs and shunts provide accurate output current measurement, they impose certain drawbacks and limitations that are undesirable.
It would therefore be desirable to provide a system and method that provides for accurate determination of an output current from a VSD or other power converter/inverter, without requiring the use of high-cost, environmentally sensitive, space consuming current sensors. It would further be desirable to provide a system and method that provides for accurate determination of an input current to a VSD or other power converter/inverter.